Simplify the following expression: $k = \dfrac{2yx}{6yx - 6zx} - \dfrac{4x^2}{6yx - 6zx}$ You can assume $x,y,z \neq 0$.
Answer: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{2yx - (4x^2)}{6yx - 6zx}$ $k = \dfrac{2yx - 4x^2}{6yx - 6zx}$ The numerator and denominator have a common factor of $2x$, so we can simplify $k = \dfrac{y - 2x}{3y - 3z}$